Mastervolt Mass GI iso transformer

[Belliure 50]

Helping a buddy out with an electrical conundrum.
He recently installed an aircon compressor after being told by an "electrician" that the old units compressor had seized. After installing the new unit, the exact same problem is still prevalent.
Issue as follows: turns AirCon unit on, it beeps, then nothing, followed by his ground fault protection breakers clack on and off 3 or 4 times, then the shore power breaker on the dock trips.
We tested the unit direct to shore power (bypassing the iso transformer and GFP breakers, and it starts and runs fine.
While chasing our tails I measured the output side of the iso trans (240VAC euro power) and saw 120VAC between earth and live, and 120VAC between earth and Neutral, which seems odd as the neutral should be tied to the boats ground as per mastervolt instructions. Am I measuring incorrectly or is it possible the Iso transformer has a problem? All other AC powered devices in the boat work fine, just the AirCon that causes problems.


Tia for any help!

[smac999]

you need to manually connect the output neutral to ground inside the isotransformer when it's installed. sounds like the installer didn't.